To allow builds of Python to be run from an in-tree layout (rather than an installed file layout), the VPATH variable is defined at build time and used to locate certain landmarks - specifically, Modules/setup.local. When this landmark is found relative to VPATH relative to the executable, Python assumes it is running in a source tree and generates a different default sys.path. This code remains in release builds, so that release-ready builds can be built in-tree. On Windows, since builds are written to 'PCbuild/', the value of VPATH is set to '..\..', which results in a landmark of '..\..\Modules\setup.local'. This path is outside the install directory of Python, and may have different permissions, potentially allowing a low-privilege user to create the landmark and an alternative `Lib` folder that will be discovered by an otherwise restricted install. Such a setup occurs with the legacy default install location for all users (in the now superseded EXE installer), due to how Windows allows all users to create folders in the root directory of their OS drive. Our recommended mitigation on Windows is to migrate away from the legacy installer and use the new [Python install manager](https://www.python.org/downloads/latest/pymanager/) to install for the current user. Installs where the directory two levels above the Python installation directory have equivalent permissions are unaffected (in general, a per-user install cannot be modified at all by other users, removing any escalation of privilege risk, and could be directly modified by a privileged user, making the potential tampering irrelevant). Alternative mitigations might include preemptively creating and restricting access to a `Modules` directory. Be aware that only 3.13 and 3.14 will receive updated legacy installers - earlier fixes are only provided as sources. Platforms other than Windows allow VPATH to be overridden, but as they don't usually use a separated directory in the build for binaries, are unlikely to have a landmark reference outside of the install directory. The landmark detection involving VPATH is a fallback for when a more specific landmark - .\pybuilddir.txt - is absent, and was included for compatibility. Future releases of Python will no longer include the fallback, and so builds will need to generate or preserve the pybuilddir.txt file in order to work in-tree. This landmark file has been generated on Windows since 3.11, and on other platforms for longer.

The AlmaLinux 9.2 host has packages installed that are affected by multiple vulnerabilities as referenced in the TuxCare ALMALINUX9.2:CLSA-2026:1790155146 advisory.

  - To allow builds of Python to be run from an in-tree layout (rather than an installed file layout), the     VPATH variable is defined at build time and used to locate certain landmarks - specifically,     Modules/setup.local. When this landmark is found relative to VPATH relative to the executable, Python     assumes it is running in a source tree and generates a different default sys.path. This code remains in     release builds, so that release-ready builds can be built in-tree. On Windows, since builds are written to     'PCbuild/', the value of VPATH is set to '..\..', which results in a landmark of     '..\..\Modules\setup.local'. This path is outside the install directory of Python, and may have different     permissions, potentially allowing a low-privilege user to create the landmark and an alternative `Lib`     folder that will be discovered by an otherwise restricted install. Such a setup occurs with the legacy     default install location for all users (in the now superseded EXE installer), due to how Windows allows     all users to create folders in the root directory of their OS drive. Our recommended mitigation on Windows     is to migrate away from the legacy installer and use the new [Python install     manager](https://www.python.org/downloads/latest/pymanager/) to install for the current user. Installs     where the directory two levels above the Python installation directory have equivalent permissions are     unaffected (in general, a per-user install cannot be modified at all by other users, removing any     escalation of privilege risk, and could be directly modified by a privileged user, making the potential     tampering irrelevant). Alternative mitigations might include preemptively creating and restricting access     to a `Modules` directory. Be aware that only 3.13 and 3.14 will receive updated legacy installers -     earlier fixes are only provided as sources. Platforms other than Windows allow VPATH to be overridden, but     as they don't usually use a separated directory in the build for binaries, are unlikely to have a landmark     reference outside of the install directory. The landmark detection involving VPATH is a fallback for when     a more specific landmark - .\pybuilddir.txt - is absent, and was included for compatibility. Future     releases of Python will no longer include the fallback, and so builds will need to generate or preserve     the pybuilddir.txt file in order to work in-tree. This landmark file has been generated on Windows since     3.11, and on other platforms for longer. (CVE-2026-12003)

  - The stringprep module didn't process characters from RFC 3454 tables B.2 or B.3 correctly: the latest     Unicode codepoint attributes were used instead of the specified Unicode 3.2.0. This behavior would cause     mismatches when processing domain names using IDNA 2003 (the idna codec) and the in_table_b2() function     of the stringprep module. This only affects domain names containing characters that were not previously     registered or had their Unicode attributes such as case-folding behavior updated since Unicode 3.2.0.
    (CVE-2026-17084)

  - The tarfile module's tar and data extraction filters created directories outside the destination for     members whose name leaves the destination and returns to it, such as ../evil/../dest/sub/file. The     containment check used the resolved path, but intermediate directories were created from the name as     given. Only empty directories are created outside the destination. Member contents are still extracted     inside it. To return to the destination the member's name must contain the destination directory's own     final component, so extraction into a secure randomised directory is not affected. This affects POSIX     platforms only. On Windows, .. components are collapsed before the path reaches the filesystem, so the     directories outside the destination are never created. (CVE-2026-19672)

  - When tarfile extracts a link on a system that doesn't support links, it falls back to extracting a member     from the archive. In this case, the filter function is run twice: once for the extracted member, and once     with name set to the location of the link. For one of the calls, the return value was ignored. Instead,     the member should be skipped if either call returns None. (CVE-2026-87910)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - To allow builds of Python to be run from an in-tree layout (rather than an installed file layout), the     VPATH variable is defined at build time and used to locate certain landmarks - specifically,     Modules/setup.local. When this landmark is found relative to VPATH relative to the executable, Python     assumes it is running in a source tree and generates a different default sys.path. This code remains in     release builds, so that release-ready builds can be built in-tree. On Windows, since builds are written to     'PCbuild/', the value of VPATH is set to '..\..', which results in a landmark of     '..\..\Modules\setup.local'. This path is outside the install directory of Python, and may have different     permissions, potentially allowing a low-privilege user to create the landmark and an alternative `Lib`     folder that will be discovered by an otherwise restricted install. Such a setup occurs with the legacy     default install location for all users (in the now superseded EXE installer), due to how Windows allows     all users to create folders in the root directory of their OS drive. Our recommended mitigation on Windows     is to migrate away from the legacy installer and use the new [Python install     manager](https://www.python.org/downloads/latest/pymanager/) to install for the current user. Installs     where the directory two levels above the Python installation directory have equivalent permissions are     unaffected (in general, a per-user install cannot be modified at all by other users, removing any     escalation of privilege risk, and could be directly modified by a privileged user, making the potential     tampering irrelevant). Alternative mitigations might include preemptively creating and restricting access     to a `Modules` directory. Be aware that only 3.13 and 3.14 will receive updated legacy installers -     earlier fixes are only provided as sources. Platforms other than Windows allow VPATH to be overridden, but     as they don't usually use a separated directory in the build for binaries, are unlikely to have a landmark     reference outside of the install directory. The landmark detection involving VPATH is a fallback for when     a more specific landmark - .\pybuilddir.txt - is absent, and was included for compatibility. Future     releases of Python will no longer include the fallback, and so builds will need to generate or preserve     the pybuilddir.txt file in order to work in-tree. This landmark file has been generated on Windows since     3.11, and on other platforms for longer. (CVE-2026-12003)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
351910	AlmaLinux 9.2 [TuxCare] Security Update: python3.11 / python3.11-debug / python3.11-devel / python3.11-idle / etc Multiple Vulnerabilities (ALMALINUX9.2:CLSA-2026:1790155146)	Nessus	Alma Linux Local Security Checks	Local	medium
321379	Linux Distros Unpatched Vulnerability : CVE-2026-12003	Nessus	Misc.	Local	medium

Detections

Analytics

CVE-2026-12003

medium

Tenable Plugins

medium

medium